What is desired from a logistics system is that it should have high efficiency, high flexibility, low acquisition cost, low operating costs as well as low environmental impact.
Rail transports are possibly comparatively environmental-friendly, but the other desires are not fulfilled other than possibly in particular transportation cases. Railway wagons are instead heavy, at the expense of the loading capacity, as well as expensive to purchase and operate.
It is also very expensive to build the railway itself, which makes that rail transports rarely can be made “from door to door”. Therefore, transhipments are needed, which considerably increases the total transport time as well as the risk of problems. In addition, in transports between different countries, different track gauges sometimes occur, which also means transhipments.
Another major reason for the disadvantages of the railway is due to railway wagons being expensive to manufacture and type approve as well as being manufactured for a specific field of application for a very long service life, normally 30 years. This service life is so long that it is not possible to have a detailed knowledge about the transportation needs for such a long time ahead. Accordingly, acquisition of railway wagons involves a very high economic risk.
Therefore, railway wagons are often formed for as many fields of application as possible. This results in wagons in the end rarely being optimal for their purpose.
In many cases with special types of cargo, it is not even possible to consider rail transports, since there are no wagons for this type of cargo, and in many cases it is too expensive and time-consuming for each individual user to develop entirely new wagons from scratch for a specific need. In other cases, it may, e.g., not be possible to take advantage of the opportunity that a certain section of a line can manage a greater wagon weight, since this very type of wagon is maybe not available.
The long service life of the railway wagons, in combination with the same being subjected to fatigue load, implies that they have to be made very solid. This makes them heavy and thereby even more expensive.
Today, there are high-strength steels by means of which it would be potentially possible to lower the wagon weights. Unfortunately, the fatigue load has also the disadvantage that it is not possible to utilize the advantages of said steel grades.
In order to considerably improve the conditions for rail transports, it would be necessary to make it possible to simply alter railway wagons for different conditions and use, drastically decrease the need of transhipments as well as make them lighter and thereby more inexpensive by minimizing the parts subjected to fatigue load.
Transportation of bulk material involves particular challenges in that it is difficult to combine a railway wagon simple in the design, and thereby inexpensive and maintenance-friendly, with a cost-effective method of unloading the cargo.
A solution is to use bottom- or side-dumping wagons. However, this makes each wagon extra complicated with movable doors. If there are numerous wagons, this implies a considerable extra cost compared with wagons without doors. The doors also involve extra maintenance costs and the risk of the mechanisms jamming. In addition, each wagon becomes heavier at the expense of the loading capacity.
The most inexpensive way to transport bulk material on railway is to use the simplest possible wagon, in principle a box on wheels. This minimizes the cost of purchase and maintenance. The problem is that said wagons are difficult to discharge in a cost-effective way.
Today, there are in principle two ways to discharge such wagons. One is to use an excavator. This solution is, however, time-consuming and wears out the wagons. Another way is to use a so-called wagon tipper. Wagon tippers work in such a way that they discharge the wagons by revolving the entire wagon together with the part of the rail on which the wagon is standing. However, these machines are very expensive to purchase and maintain. In addition, each wagon has to be provided with expensive and delicate rotatable couplers. Such ones are not even approved in Europe. In addition, the solution has the disadvantage of it being dangerous to clean wagons having sticking cargo, since this is effected with the wagons upside-down. Particular, expensive machines are also required for the positioning of the train, since the locomotive cannot position the wagons in the unloading station with the precision required.
By U.S. Pat. No. 1,940,732, a railway wagon is known, the cargo carrier of which can be tilted sideward by means of a hydraulic cylinder, which is arranged to act on one long side of the cargo carrier. An axis of rotation, around which the cargo carrier is disposed to be tilted, is, however, positioned on the chassis of the railway wagon, which entails that the cargo body cannot be tilted at such a great angle as desirable, particularly in the case of sticking cargo.
By DE 1151219 B, a device is known for discharging a cargo carrier loosely carried on a railway wagon by rotating the same.